Commit 87ccc826 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/unwind/orc: Change REG_SP_INDIRECT 



Currently REG_SP_INDIRECT is unused but means (%rsp + offset),
change it to mean (%rsp) + offset.

The reason is that we're going to swizzle stack in the middle of a C
function with non-trivial stack footprint. This means that when the
unwinder finds the ToS, it needs to dereference it (%rsp) and then add
the offset to the next frame, resulting in: (%rsp) + offset

This is somewhat unfortunate, since REG_BP_INDIRECT is used (by DRAP)
and thus needs to retain the current (%rbp + offset).

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
parent 9077c016

arch/x86/kernel/unwind_orc.c

+4 −1
Original line number Diff line number Diff line
@@ -471,7 +471,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		break;



	case ORC_REG_SP_INDIRECT:

		sp = state->sp + orc->sp_offset;

		sp = state->sp;

		indirect = true;

		break;
@@ -521,6 +521,9 @@ bool unwind_next_frame(struct unwind_state *state) 
	if (indirect) {

		if (!deref_stack_reg(state, sp, &sp))

			goto err;



		if (orc->sp_reg == ORC_REG_SP_INDIRECT)

			sp += orc->sp_offset;

	}



	/* Find IP, SP and possibly regs: */

tools/objtool/orc_dump.c

+1 −1
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ static void print_reg(unsigned int reg, int offset) 
	if (reg == ORC_REG_BP_INDIRECT)

		printf("(bp%+d)", offset);

	else if (reg == ORC_REG_SP_INDIRECT)

		printf("(sp%+d)", offset);

		printf("(sp)%+d", offset);

	else if (reg == ORC_REG_UNDEFINED)

		printf("(und)");

	else